The invention relates to a power mover for use in a mobile irrigating system and more particularly to a power mover connected in the center of a line of coupled wheel-mounted irrigating pipes.
Various types of power movers are used in mobile irrigating systems. In some such systems a plurality of hydraulic motors are provided along a length of the coupled irrigating pipes to move the pipes. In other systems lengths of wheel-mounted irrigating pipes which carry sprinkler heads are coupled together in a long line to be rolled across the field to be irrigated. In order to provide the motive power to rotate the line of wheeled irrigating pipes, a power unit is connected in the middle of the line of irrigating pipes.
The centralized power unit applies a torque to the wheel-mounted pipes through a motor-driven bull gear which is mounted on a wheeled carriage which straddles the pipe. Driving power is usually also provided to the wheels of the carriage as well as to the bull gear.
All prior art mobile irrigating systems suffer from a number of disadvantages involving loss of power, maintenance, or inconvenient controls. For example, in order to allow the driving torque to be reversed in some systems the motor turns the bull gear through a hydraulic drive assembly. One problem in such types of movers is that there can be a high degree of maintenance required in the hydraulic pump for it to operate properly. In still other systems rotational power from a motor at the side end of the pipes is coupled to two or more planetary transmissions on the central unit via a drive shaft which extends along the length of coupled pipes. One disadvantage of this type of system is in frictional losses, particularly when the line of irrigating pipes becomes misaligned or slightly bent as the system is moved across the field.
In systems having a centralized power mover with an internal combustion engine the operator must walk out to the midpoint of the line of pipes, which may be as long as 1/8 to 1/4 of a mile, and then start the engine in the desired direction and walk with the assembly until it has reached the new position. He must then stop the engine and walk back out to the end of the line of pipes and couple it up to the water supply system. In farm operations where labor is scarce or expensive, such as requirement becomes highly undesirable because it needlessly consumes a relatively large amount of time by the worker.
In many mobile irrigation systems, since the sprinkler heads are attached directly to the lengths of rotating pipe, alignment can be a critical problem since the entire line of coupled pipes must be rotated to the new position and stopped at exactly the point where the sprinkler heads are pointed in the proper direction so that they will properly irrigate the field. This sometimes requires a certain amount of jockeying of the power mover. In systems having hydraulic drives this is accomplished by reversing the flow of hydraulic fluid to the drive. In systems utilizing a direct drive, internal combustion engine, however, this jockeying is much more difficult to carry out. One system attempts to overcome this problem by utilizing the technique described above of a drive shaft mounted on the pipes to transmit power to the central unit from a hand-held engine connected to the drive shaft at the end of the coupled pipes nearest the side of the field. The system is made reversible simply by providing couplings on both ends of the engine drive shaft. To reverse the direction of travel the engine is uncoupled from the pipe-mounted drive shaft, turned 180.degree. and recoupled to the pipe-mounted drive shaft. A major disadvantage of this system is that the engine must be physically lifted by the operator, thus precluding its operation by most women and children. Since women and older children often work on family-owned farms, this advantage makes the use of such a system on a family-owned farm uneconomical.
It is necessary for all these systems to operate over an entire season with a minimal amount of maintenance. Electric drive motors are thus extremely impractical, first because of the difficulty in properly insulating them from the water spray, and secondly because of the weight of the batteries which would be required to power the unit through an entire season. Even with an internal combustion engine the problem in some systems of keeping the unit powered throughout an entire season can be vexing since fuel must usually be carried out to the middle of the field.